<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>噪声生成复杂的纹理-实现噪声函数（一维）</title>
    <style>
        canvas{
            border:1px solid #ccc;
        }
    </style>
</head>
<body>
    <canvas width="554" height="554"></canvas>

    <script src="/common/lib/gl-renderer.js"></script>

    <script type="module">
        import { grayMatrix } from "/review/common/lib/utils.js"

        /**
         * 1.创建renderer对象
         * 2.创建webgl程序
         * 3.创建uniform变量
         * 4.将数据存入缓冲区
         * 5.渲染
         * */ 

        //  1.
        const canvas = document.querySelector("canvas");
        const renderer = new GlRenderer(canvas);

        (async function(){
            // 2.
            const vertex = `
                attribute vec2 a_vertexPosition;
                attribute vec2 uv;
                varying vec2 vUv;

                void main(){
                    vUv = uv;
                    gl_Position = vec4(a_vertexPosition, 1.0, 1.0);
                }
            `;
            const fragment = `
                #ifdef GL_ES
                    precision mediump float;
                #endif

                varying vec2 vUv;

                // 随机数
                // float random(vec2 st){
                //     return fract(sin(dot(st.xy, vec2(12.9898, 78.233))) * 43758.5453123);
                // }
                // 一维随机数
                float random(float x){
                    return fract(sin(x * 1243758.5453123));
                }
                // 一维噪声
                float noise(float x){
                    float i = floor(x);
                    float f = fract(x);
                    return mix(random(i), random(i + 1.0), smoothstep(0.0, 1.0, f));
                }

                void main(){
                    vec2 st = vUv - 0.5;
                    st *= 10.0;

                    float d = noise(st.x);
                    d = smoothstep(st.y - 0.05, st.y, d) - smoothstep(st.y, st.y + 0.05, d);

                    gl_FragColor.rgb = vec3(d);
                    gl_FragColor.a = 1.0;
                }
            `;

            const program = renderer.compileSync(fragment,vertex);
            renderer.useProgram(program);

            // 3.
            
            // 4.
            renderer.setMeshData([{
                positions:[
                    [-1, -1],
                    [-1, 1],
                    [1, 1],
                    [1, -1],
                ],
                attributes:{
                    uv:[
                        [0, 0],
                        [0, 1],
                        [1, 1],
                        [1, 0],
                    ]
                },
                cells: [[0, 1, 2], [2, 0, 3]],
            }]);

            // 5.
            renderer.render();
        })();
        
    </script>
</body>
</html>